Servlet 4, Tomcat 9 vs. Tomcat 10 and later

[kasemir]

The PWVS has been developed for the Servlet 4 API (javax.servlet.* classes) which is supported up until Tomcat 9.

With Tomcat 10, the Servlet API has switched to jakarta.servlet.* packages, resulting in errors similar to

java.lang.NoClassDefFoundError: javax/servlet/ServletContextListener

When we update the source code to the newer Servlet spec, this will break usage on older but still supported tomcat versions.
For now, the solution is to run on Tomcat 9, not Tomcat 10.

[kasemir]

tomcat10 branch allows building for Servlet 5 API